From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dmitry Vyukov , Paul Bolle , Tilman Schmidt , "David S. Miller" , Sasha Levin Subject: [PATCH 4.4 022/114] ser_gigaset: use container_of() instead of detour Date: Thu, 8 Nov 2018 13:50:37 -0800 Message-Id: <20181108215101.164658460@linuxfoundation.org> In-Reply-To: <20181108215059.051093652@linuxfoundation.org> References: <20181108215059.051093652@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit List-ID: 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ [ Upstream commit 8d2c3ab4445640957d136caa3629857d63544a2a ] The purpose of gigaset_device_release() is to kfree() the struct ser_cardstate that contains our struct device. This is done via a bit of a detour. First we make our struct device's driver_data point to the container of our struct ser_cardstate (which is a struct cardstate). In gigaset_device_release() we then retrieve that driver_data again. And after that we finally kfree() the struct ser_cardstate that was saved in the struct cardstate. All of this can be achieved much easier by using container_of() to get from our struct device to its container, struct ser_cardstate. Do so. Note that at the time the detour was implemented commit b8b2c7d845d5 ("base/platform: assert that dev_pm_domain callbacks are called unconditionally") had just entered the tree. That commit disconnected our platform_device and our platform_driver. These were reconnected again in v4.5-rc2 through commit 25cad69f21f5 ("base/platform: Fix platform drivers with no probe callback"). And one of the consequences of that fix was that it broke the detour via driver_data. That's because it made __device_release_driver() stop being a NOP for our struct device and actually do stuff again. One of the things it now does, is setting our driver_data to NULL. That, in turn, makes it impossible for gigaset_device_release() to get to our struct cardstate. Which has the net effect of leaking a struct ser_cardstate at every call of this driver's tty close() operation. So using container_of() has the additional benefit of actually working. Reported-by: Dmitry Vyukov Tested-by: Dmitry Vyukov Signed-off-by: Paul Bolle Acked-by: Tilman Schmidt Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- drivers/isdn/gigaset/ser-gigaset.c | 9 +-------- 1 file changed, 1 insertion(+), 8 deletions(-) diff --git a/drivers/isdn/gigaset/ser-gigaset.c b/drivers/isdn/gigaset/ser-gigaset.c index 74bf1a17ae7c..b90776ef56ec 100644 --- a/drivers/isdn/gigaset/ser-gigaset.c +++ b/drivers/isdn/gigaset/ser-gigaset.c @@ -373,13 +373,7 @@ static void gigaset_freecshw(struct cardstate *cs) static void gigaset_device_release(struct device *dev) { - struct cardstate *cs = dev_get_drvdata(dev); - - if (!cs) - return; - dev_set_drvdata(dev, NULL); - kfree(cs->hw.ser); - cs->hw.ser = NULL; + kfree(container_of(dev, struct ser_cardstate, dev.dev)); } /* @@ -408,7 +402,6 @@ static int gigaset_initcshw(struct cardstate *cs) cs->hw.ser = NULL; return rc; } - dev_set_drvdata(&cs->hw.ser->dev.dev, cs); tasklet_init(&cs->write_tasklet, gigaset_modem_fill, (unsigned long) cs); -- 2.17.1